Fuse construction



Oct. 16, 1951 w. o. scHULTz FUSE CONSTRUCTION 2 Sheet's-Sheet l Filed Feb. 21, 1948 Oct. 16, 1951 w. o. scHuLTz FUSE CONSTRUCTION 2 Sheets-Sheet 2 Filed Feb. 2l, 1948 Nw m R Sv l-'Iilll nl. NM

Patented Oct. 16, 1951 FUSE CONSTRUCTION William O. Schultz, South Milwaukee, Wis., assignor to McGraw Electric Company, a corporation of Delaware Application February 21, 1948, Seria-l No. 10,040

Claims.

This invention relates to fuse constructions.

Objects of this invention are to provide a fuse construction in which a transparent discolorable member, such for instance, as a cylinder is arranged within a transparent container and surrounds a fuse link and is so arranged that when the fuse link blows, the discolorable member will indicate that the fuse link has blown and the fuse cartridge can, therefore, be discarded and a new one substituted therefor.

In greater detail, further objects are to provide a cartridge type of fuse in which a transparent outer cylinder is provided and within which a cylinder of clear acrylic plastic such, for example, as that commonly known as Lucite, is positioned and surrounds the fuse link and in which arc extinguishing material is located on opposite sides of the discolorable cylindrical member, such material being adapted to chill the arc and to provide a cooling and expansion chamber on each side of a gas evolving substance so as to permit the interruption of large currents ai; high voltage although the fuse construction constitutes merely a cartridge type of enclosed fuse of reasonable dimensions.

Further objects are to provide a construction in which a discolorable member is positioned and is arranged to indicate at all times the state of the fuse link, and in which means are provided for insuring the extinction of the arc and the chilling of any fulgurite or other semi-conduct- `ing fused section that may be formed in the chilling or cooling material so that the conducting quality of such path is quickly destroyed.

Further objects are to provide a cartridge type fuse in which means are provided for insuring Kthe correct positioning and retention of the arc 'extinguishing material and of the discolorable member and of the fuse link itself and to provide such a construction as can be easily manufactured and assembled.

Embodiments of the invention are shown in the accompanying drawings, in which:

Figure 1 is a sectional view through a fuse construction showing one form that the invention may take.

Figure 2 is a sectional view on the line 2 2 of Figure 1.

Figure 3 is a sectional view on the line 3-3 of Figure l.

Figure 4 is a detail of the barrier washer.

Figure 5 is a sectional view through one of the sealing rings.

Figure 6 is a perspective view of one of the end ttings for holding the central rod.

(Cl. ZOU- 121) Figure 7 is a view corresponding to Figure 1 showing a further form of the invention.

Figure 8 is a sectional view on the line 8-8 of Figure '7.

Figure 9 is a sectional View on the line 9--9 of Figure 7.

Figure 10 is a perspective View of the indicating cylinder.

Referring to the iirst form of the invention, shown in Figures 1 through 6, it will be seen that the fuse construction comprises a transparent outer tubular casing I of glass or similar material having end caps 2 and 3 provided with terminal portions 4 and 5 and with locking screws or set screws 6, E.

The end caps 2 are secured in place by means of a low melting point alloy 'I or any other suitable sealing compound, and preferably suitable gaskets 8 are interposed between the ends of the tubular member I and the end caps 2.

A ribbed or other shaped ceramic rod 9 is positioned centrally of the tubular transparent casing or housing I and is supported at its end by means of ttings I0 which are suitably slotted as indicated at II, see Figure 6, and are provided with projecting stems or rods I2. These rods I2 are received in apertures I3 formed in the end caps 2 and 3 and are locked in place by means of the set screws or locking screws 6. If desired, the ends of the rods I 2 and apertures I3 may be soldered over as indicated at I4 to seal the openings I3 after the rods I2 have been inserted and secured by the screws 6.

A fuse wire I5 is wound around the ceramic supporting rod 9 and is secured at its ends in any suitable manner to the iittings I0.

Centrally of the transparent tubular member I a cylindrical member I6 of a clear acrylic plastic, such as Lucite, is positioned. The cylindrical member I6 is provided with reduced portions I9 on which rubber washers Il are positioned. These rubber washers I'I have thin flanges I8 which readily yield and accommodate any variation of the diameter of the tubular housing I, as it has been found that due to manufacturing errors, the diameter of the members I vary. The purpose of the rubber washers I1 is to keep bauxite, hereinafter referred to, from sifting into the space between the transparent cylindrical member I6 and the transparent housing I.

The housing is iilled with material in the following manner: As viewed in Figure l the housing or shell I is held vertically with the right hand end down and with the rod 9 and cylindrical 'member I6 properly held in place by means not shown, and with the barrier washer 2| in place against the now upper end of the cylindrical member I5. The tube is lled above the washer 2l with powdered bauxite 2G, the washer 2| preventing the bauxite from seeping through the opening 22 in the cylindrical member I6. Thereafter sand 23 is poured into the upper end of the housing and a plaster of Paris seal 25 is formed to hold the granular or powdered material in place.

The housing is now inverted and bauxite 25 is poured into the other end of the housing, the

bauxite nlling the space 22 within the transparent cylinder l5 and lling the housing l to the point indicated in the drawings. Sand 23 is now poured into the housing and the plaster of Paris seal 2li is formed at the now upper end of the housing The bauxite is preferably powdered, as stated, and the sand preferably a ne grained cutting sand.

The end caps 2 are secured in'place aiter'the housing i' has been'illed andthe plaster-of'Paris seals 2li formed.,

It is to be noted that the fuse link I5 isin close proximity to the surfacey of' the apertureZZof the transparent cylinder l5. Y

The clear'acry-lic plastic cylinder l5 has been found to have a peculiar action. When the inse link blows it discolors the interior of the tra-nsparent plastic cylinder l5 and forms a-distinc" tivepattern which is readily observable from the outsidev of the transparent casingor housing Although a fuse link of ccnsiderablevlengthis employed, it has been found that substantially uniformly, the blowing or rupturingrof the fuse link occurs centrally of theffuse construction. 1t has been found also that due'to'the curvature or cylindrical formation of the plastic cylinder |5, a magnifying. eifect is produced which further enhances cr augmente the visibility or ease with which detection of -a blown fuse may be had.

It is intended that the entire fuse cartridge shall be discarded after the fuse linkhas-,blown and anew cartridge substituted.

It has been found that when the. fuse link blows, that-the bauxite 25 releases a quantity of vapor, including water vapor, and this tends to chillor cool theA arc. `Further the sand 23 provides an expansion area for the gases generated by theblowing oi the fuse link and provides. a vast or extended Ysurface to actas a cooling, surface for the hot gases. Under-certain conditions. a ful-- gurite is formed in the sand .upon the rupture ci the. fuse link. The water vapor liberated Vbythe bauxite quickly chills this V'fulgurite andprevents it from reaching a temperature so high that it would become a conductonsupport the arc and cause failure of the device.

It has beeniound that although the fuse construction is of a cartridgev type, that nevertheless it is satisfactory ior use in interrupting large currents at `high voltage without generating an excessive gas pressure within the cartridge.

A further Vform of the invention is shown in Figures' through l0. En this form ofr the invention the outer tubular casing or housing indicated atY 25 may be of ber, Bakelite, or other suitable Vnon-transparent material. One end ofk the outer tubular member Z5 is provided with a tting 25 with a ange which is centrally apertured as indicated at 2. A threaded metal member 28'extendsl through Vthe aperture 2'? and is provided with inwardly located anges 29. It is provided with a hood or shield portion 55 which is cut out on its under side as'shown most clearly in Figure 9. The threaded portion 23 receives a nut 3| which clamps one of the terminal members 32 in place. The hood-like member 3U extends downwardly and may have a curved outer end as indicated at 32. It houses a clear acrylic plastic cylindrical member 33 which is provided with a small central aperture 3d. This cylindrical member 33 is visible from the cutaway portion 30', see Figure 9, of the hood-like'part Si).

The other end of the tubular end of casing 25 is provided with a cup-shaped end tting 35 o metal which is clamped in place by means of a screw 3&5v and nut 37 to a terminal member 38. The cup-shaped member S5 is held in place by a ianged errule or cylindrical member 35 which is screw threaded onto the casing 25. A ribbed, ceramic central member i5 is positioned within the outer tubular member 25 and one end is received in a tubular metal end piece @I which is secured to a flexible braided conducting strip 52 and which is urged inwardly by means of a spring d3.Y The flexible tape or conducting member d2 is clamped between the end ofthe tubular -member Z5 and the conductingcup-shapedmember 35. The spring 13S. urges the ceramic.Y rodll to the left as viewed in Figure 7 against an asbestos washer e4 which bears against a conically apertured nber member t5. The nber member 45, in turn, bears against the indicating transparent cylinder 33 hereinbefore described.

A fuse link i5 is wrapped around the ceramic supporting central member i5 as indicated and. one end is secured to the metallic holding member 4| and the other end to a plugvll, which is received in an aperture 48 formed in the hoodlike portion 32 of the member 30 and soldered in place as indicated at iS- The central portion of the tubular member 25 is filled with powdered bauxite 5]- and the, end areas of the tubular member 25 are nlledwith sand 5|. The sand 5| may bea nne grained, cuttingY sand as previously described, such as the sand used for sand blasting for instance.

On overload, particularly onrelatively heavy overload, the fuse link t6 melts throughout'its length and the action of the bauxite 50 and sand 5| is identically as previously described. The fusing of the fuse. linkt@ Ywithinvthe aperture 34 .of the clear, acrylic plastic cylinder 33, such for instance as- Lucite,` gives thediscoloration hereinbefore describedand indicatesthat th fuse. has blown. Y

The rst form of the invention shown in Figures 1 through 511s the preferredform, although the form shown in Figure 7 can be satisfactorily used as hereinabove described, andif thefuse link is of uniform cross-section throughout, it isrprimarily intended for relatively heavy overloads. On the other hand, it is within the province of this invention to form the section of the fuse link i5 of Figure 7 of a reduced cross-sectional area in the point where it passes through the cylinder 53 so as to insure rupture at this point as well as at other points along the length of the fuse link.

The rst form of the invention'is the preferred form for another reason. It has been found that when the fuse blows in either form ofthe invention, that there is discoloration of the clear acrylic plastic. However, it has been found that when bauxite is present within the -clear acrylic plastic cylinder I5 in the rst form of theV invention as is shown in Figure 3, that there is an increase in the discoloration or, in other words, the discoloration is more pronounced.

It has been found that as the. melting point of 5 the fuse link is approached, the polished inner surface of the plastic cylinder I6 melts and causes the bauxite to stick and possibly absorb some of the liquid plastic. This gives a very distinct discoloration which is more pronounced than if no bauxite is present.

The porcelain or other refractory supporting rod for the fuse link shown in both forms of the invention could be omitted for fuses arranged for lower voltages as the fuse link would be heavier and need not necessarily be supported. However, for higher voltages it is diicult to handle and control the fuse wire mechanically during the filling operation and for this reason the refractory supporting rod for the fuse link offers the simplest and best solution.

In both forms of the invention the cylindrical plastic discolorable indicating cylinder has somewhat of a magnifying effect and makes it easier to see that the interior surface has been discolored upon blowing of the fuse link.

It has been found that fuses constructed in accordance with this invention are capable of handling larger overloads without venting any of the gases to the outside and yet Without subjecting the external casing to excessive internal pressure.

It will be seen further that the fuse constructions are of simple type and may be readily produced and assembled.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. A fuse construction comprising a tubular casing, terminals adjacent opposite ends thereof, a fuse link within said tubular casing and electrically connecting said terminals, and an acrylic plastic cylinder surrounding a portion of said fuse link and characterized by the fact that it will discolor upon rupture of said link, said construction including transparent means adjacent said plastic cylinder, said. plastic cylinder being visible from the exterior of said casing.

2. A fuse construction comprising a transparent tubular outer casing, terminals adjacent opposite ends thereof, a fuse link electrically connecting said terminals and extending through said casing, and a. clear acrylic plastic cylinder located within said casing and surrounding a portion of said fuse link and characterized by the fact that it discolors upon rupture of said fuse link.

3. A fuse construction comprising a transparent tubular outer casing, terminals adjacent opposite ends thereof, a clear acrylic plastic cylinder within said casing and visible through said casing, a fuse link electrically connecting said terminals and located within said casing and having an intermediate portion extending through said cylinder, powdered bauxite within said casing and located on opposite sides of said cylinder, and sand within said casing located on opposite sides of said bauxite.

4. A fuse construction comprising a transparent tubular outer casing, terminals adjacent opposite ends thereof, a clear acrylic plastic cylinder within said casing and visible through said casing, yielding washers surrounding end portions of said cylinder and wedging against the interior surface of said casing, a fuse link electrically connecting said terminals and located within said casing and having an intermediate portion extending through said cylinder, powdered bauxite within said casing and located on opposite sides of said cylinder, and sand within said casing located on opposite sides of said bauxite.

5. A fuse construction comprising a transparent tubular outer casing, terminals adjacent opposite ends thereof, a clear acrylic plastic cylinder within said casing and visible through said casing, a fuse link electrically connecting said terminals and located within said casing and having an intermediate portion extending through said cylinder, powdered bauxite within said casing and having portions located on opposite sides of said cylinder and having a portion located within said cylinder, and sand within said casing located on opposite sides of said bauxite.

WILLIAM O. SCHULTZ.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 636,379 Erikson Nov. '1, 1899 856,292 Phelps June 11, 1907 948,296 Schattner Feb. 1, 1910 1,033,754 Buchanan July 23, 1912 1,097,964 Banks May 26, 1914 1,140,953 Cole May 25, 1915 1,917,407 Tucker July 11. 1933 2,253,719 McMahon Aug. 26, 1941 2,442,216 Skeats May 25, 1948 2,500,808 Dryer Mar. 14, 1950 

